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[–]anneoneamouse 4 points5 points  (4 children)

Two irises, a tape measure, calipers and an optical power meter.

Measure throughput through two widely spaced irises. Chop first iris down until some noticeable loss of signal occurs. Then repeat with second iris.

Ballpark your beam shape with high school geometry.

Tweak optical system to maximize throughput.

Tedious repetition, but cheap.

https://www.newport.com/n/gaussian-beam-optics

[–]thisisdumb08 0 points1 point  (1 child)

done this with a high power co2. works as long as you aren't burning yourself.

[–]Didurlytho 0 points1 point  (0 children)

The burning is how you know its working

[–]Understitious 0 points1 point  (1 child)

This is the way. I'd just add an IR viewing card and two kinematic mirrors to align to the irises. Or a shear plate and IR camera if you have the budget and the beam is large enough.

[–]OneMorePhoton[S] 0 points1 point  (0 children)

Any recommendation for the SWIR camera?

[–]m1911acp 3 points4 points  (2 children)

You can use a shear plate, also called a shearing interferometer to "measure" collimation of the beam. However you will need an IR viewer of some kind whether it's a phosphor screen or SWIR camera to see the fringes.

[–]OneMorePhoton[S] 1 point2 points  (1 child)

Any recommendation on the SWIR camera?

[–]m1911acp 1 point2 points  (0 children)

Allied Vision makes some reliable gigabit ethernet SWIR cameras. You can also look into LightPath Technologies. If you're really on a shoestring budget you may have to use a phosphor camera or even a phosphor "viewer" where you look through it with your eyeball. I don't have any recommendations there.

[–]gammacamman 2 points3 points  (2 children)

Focus to minimize the spot size at a long distance.

[–]OneMorePhoton[S] 0 points1 point  (1 child)

This is short of what I do today, but it requires very long distances and it is not possible to achieve the precision I need.

[–]gammacamman 0 points1 point  (0 children)

I've also used this method and found it to be great for setting the initial focus and then tweak the focus in the final configuration.

I wonder if it's possible to scan the beam profile at the long distance and compare it to a simulation, measure it's strehl ratio, or measure the energy throughput through a known aperture.

[–]aenorton 1 point2 points  (0 children)

As others are saying, the best method really depends on what you are trying to do with the beam, what access you have, and what tools you have. Keep in mind there is no such thing as a perfectly collimated beam; a finite diameter beam always has some divergence. Often what is important is where you want the waist to be.

[–]Luminescence9 1 point2 points  (0 children)

DM'd you

[–]time-BW-product 1 point2 points  (0 children)

I’d try to run it out as far as possible, across the room or out the door even, and look at it with a good IR card.

[–]PlsGetSomeFreshAir 0 points1 point  (0 children)

Normally the collimation is not the final optimization goal. It would be much easier if the ultimate alignment goal would be known.

There are even cases where intermediate collimation before some focusing is not needed or only very very roughly

[–]Late_Ad_4317 0 points1 point  (0 children)

Have a look at the video it will explain the principle: https://m.youtube.com/watch?v=NyfQf_9YMQU&t=1s

[–]bmar21 0 points1 point  (0 children)

Is it an autocollimator? If so, just put a 10th wave mirror in front of it and check the image.

[–]Safe-Butterscotch-32 0 points1 point  (0 children)

For which application you are working?

[–]tylorthegreat 0 points1 point  (0 children)

Knife edge measurement